An understanding of how surface energy is partitioned at a location is critical to gaining insight into the boundary layer meteorology and climatology of that site. Of particular relevance in the urban environment is the role of the storage heat flux, since it is believed to be a major contributor to the urban heat island effect, and is also thought to be highly dependent on the type of urban surface material (Taha 1997). Knowledge of heat storage is also required in other applications; for example, to model evapotranspiration, sensible heat flux, and boundary layer growth (Grimmond and Oke 1999). Given the complex nature of the urban surface and the inherent challenges associated with direct measurement of the storage heat flux this term has been understudied. As a matter of convenience and for lack of a better method, the storage heat flux has been calculated as the residual of the energy balance equation. Additional estimates of the urban storage heat flux have been made via parameterization schemes, in which values of the storage heat flux are parameterized in terms of a point-source net radiation value and surface material characteristics. Attempts have also been made to model energy storage within the urban environment using 1-dimensional heat transfer approaches. Unfortunately, however, most of these efforts have been performed at the micro-scale, rather than at the relevant local scale. The purpose of this paper is to investigate urban energy storage of a densely built-up downtown Mediterranean city center . The discussion focuses on the evaluation and comparison of the four approaches (direct measurement, residual method, parameterization and modeling) used to estimate and/or measure the urban energy storage flux at a site in Marseille, France. Preliminary model, parameterization, and direct measurement results from an intensive field campaign conducted in June-July 2001 will be presented.